It's not something we should be shooting for, but we're on a bit of a hot streak when it comes to global temperatures. Newly released data on the Earth's climate has revealed that 2016 saw the hottest May on record, marking the 13th successive time a monthly global temperature record has been broken as the atmospheric concentration of carbon dioxide, the main reason for this warming trend, hits new levels over the South Pole.

The data released by NASA and the US National Oceanic and Atmospheric Administration (NOAA) shows average global temperatures for May over land and ocean surfaces were 0.87° C (1.57° F) higher than the 20th century average of 14.8° C (58.6° F). This surpassed the previous record set in May 2015 by 0.02° C (0.04° F).

Temperature records have tumbled over the past year or so. Across 2015, average global temperatures were 0.76° C (1.4° F) higher than the 20th century average, and a whole degree (1.8° F) higher than the 19th century average. NOAA's records show this is the 13th consecutive month where the mercury has hit new heights for that particular time of year.

A strong El Niño pattern, which allows stored heat to escape from the ocean and influence temperatures and weather patterns, has been a factor in these record-breaking figures, but scientists say that mounting carbon emissions are the underlying reason.

"The state of the climate so far this year gives us much cause for alarm," says David Carlson, Director of the World Climate Research Programme. "Exceptionally high temperatures. Ice melt rates in March and May that we don't normally see until July. Once-in-a-generation rainfall events. The super El Niño is only partly to blame. Abnormal is the new normal."

When it comes to carbon dioxide in the atmosphere, 350 parts per million (ppm) is the concentration that experts consider safe. But the continued burning of fossil fuels has pumped so much excess CO2 into the atmosphere that concentration has risen beyond the 400 ppm mark at different monitoring stations around the world. Now, NOAA is reporting that the South Pole is the latest location to be tipped over this symbolic, and dangerous, threshold for the first time in four million years.

"The far Southern Hemisphere was the last place on earth where CO2 had not yet reached this mark," says Pieter Tans, the lead scientist of NOAA's Global Greenhouse Gas Reference Network. "Global CO2 levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer."

But it is the opposite end of the globe that is really feeling the heat, according to the World Meteorological Organization. It describes the snow cover in the Northern Hemisphere as exceptionally low and reports an earlier than normal annual melting of Arctic sea ice, along with the Greenland ice sheet.

"The rapid changes in the Arctic are of particular concern," says Carlson. "What happens in the Arctic affects the rest of the globe. The question is will the rate of change continue? Will it accelerate? We are in uncharted territory."